Communications systems

ABSTRACT

A communications system comprises a terminal, and network resources. The terminal is operable to transmit substantially simultaneously a data portion and a data transfer request for that data portion to the network resources.

RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.12/064,518, filed Jul. 8, 2008, which is a National Stage Entry ofPCT/EP2005/009059, filed Aug. 22, 2005, the contents of which areincorporated herein by reference.

The present invention relates to communications systems, and, inparticular, to 3G (third generation) networks and evolutions of suchnetworks.

BACKGROUND OF THE INVENTION

In wireless radio frequency (RF) communications networks, multiple userscommunicate using a number of specific radio channels. FIG. 1 of theaccompanying drawings illustrates a part of RF communications network 1that includes network resources 3 which communicate with mobileterminals 5, using an air interface 7. The air interface 7 defines anumber of radio channels for enabling transfer of data between thenetwork resources 3 and the mobile terminals 5. Transmissions from thenetwork resources 3 to the user 5 are ‘downlink’ communications, whilsttransmissions from the mobile terminals 5 to the network resources 3 are‘uplink’ communications. It will be readily appreciated that the term“network resources” is intended to encompass any suitable equipment inthe mobile telecommunications network. For example, the networkresources may be provided by a base station, a radio network controller(RNC) a network server, or any combination of these and other units.

When the network supports multiple users, it is necessary to controltransmissions on the radio channels to avoid signal and data loss.Downlink transmissions are relatively straightforward to control sincethe network resources 3 have all relevant information concerning theusers which it is serving, and so can control transmissions to the usersitself. However, uplink communications are more difficult to control,since an individual user does not have information concerning the otherusers that are in communication with the network resources 3. It istherefore desirable to provide a technique that controls transmissionsby the mobile terminals 5.

A Multiple Access Control (MAC) protocol is such a technique. Desiredcharacteristics of a MAC protocol include low delay and high aggregatethroughput or capacity. Previously considered MAC protocols can bedivided into two groups: conflict-free, or ‘scheduled’ protocols, andcontention-based protocols. Conflict-free protocols ensure thattransmissions do not interfere with one another. With contention-basedprotocols collisions between transmissions can occur, and principles forresolving such conflicts must be defined.

Conflict-free protocols typically involve some signalling before data istransmitted to ensure that the transmission will not conflict with othertransmissions. Although the duration of this signalling phase may beshort, the delay may represent large fractions of the total transmissiontime, especially for transmission of small amounts of data. For largeamounts of data the duration of the signalling phase is of lessimportance. However, since many data transmissions may be short, thesignalling delay can be significant. One benefit of conflict-freeprotocols is that full medium usage can be achieved. This results in ahigh capacity potential.

Contention-based protocols allow direct transmission attempts, withoutprevious signalling to ensure that the medium is free. This leads tovery low delays. However, the risk of collisions between transmissionattempts increases as load increases. Such collisions increase possibledelays. Collisions also lead to the radio channels being frequencyoccupied by non-successful transmission attempts, which in turn resultsin poor aggregate throughput.

For low traffic loads the contention-based protocols generally yieldlower delays, whereas for high traffic loads, the conflict-freeprotocols are better. Recent developments aim at combining the positiveproperties of both types of schemes by using two modes, i.e.contention-based transmission is used at low load and scheduledtransmission is used for high load.

Currently work is ongoing to design the system concepts for a long termevolution of WCDMA (wideband code division multiple access) networks.This work is also referred to as evolved UTRAN, or E-UTRAN. A strongcandidate for the air interface in E-UTRAN is Orthogonal FrequencyDivision Multiple Access (OFDMA) for the downlink and FDMA (frequencydivision multiple access) with variable bandwidth for the uplink. In thefollowing, reference will be made to OFDMA and E-UTRAN, but thesereferences should not be construed at limiting.

The E-UTRAN uplink is likely to rely mainly on scheduling, i.e. thenetwork allocates certain chunks to each user for uplink datatransmission through scheduling grants transmitted in downlink. Thenetwork typically base the issued grants on received scheduling requestsfrom the users. That means that a request phase is needed prior touplink data transmission that creates some delay. Still, some ways tosend at least scheduling requests without a prior request will beneeded.

SUMMARY OF THE PRESENT INVENTION

In an embodiment of the present invention, the mobile terminal isallowed to send data in a contention based way but simultaneously alsosends a scheduling request. If there is a collision on the contentionbased data channel, the scheduling request is likely to be received andthe network can schedule the mobile terminal with minimum schedulingdelay. In case there is no collision on the contention based datachannel the data is received in the network with a minimum delay.

In one example, there are no contention-based retransmissions; allretransmissions are under control of the scheduler.

In one example, the amount of resources allocated to contention-basedtransmission can vary over time depending on the system load and istypically reduced when the load is high.

According to one aspect of the present invention, there is provided amethod for transmitting data between a terminal and network resources ina communications network, wherein a terminal transmits a data portionsubstantially simultaneously with a data transfer request relating tothe data portion.

According to another aspect of the present invention, there is provideda communications system comprising a terminal; and network resources,wherein the terminal is operable to transmit substantiallysimultaneously a data portion and a data transfer request for that dataportion to the network resources.

In one embodiment of the present invention, a data portion and a datatransfer request are transmitted substantially simultaneously from aterminal to network resources, the data transfer request relating to thedata portion, if the data portion is not received completely by thenetwork resources, a scheduling message is transmitted from the networkresources to the terminal, and the data portion is transmitted from theterminal to the network resources according to a schedule determined bythe scheduling message.

In an embodiment of the present invention, the terminal performscontention-based data transmission to the network resources, and,substantially simultaneously, submits a data transfer scheduling requestto the network resources.

The data transfer request may include an indication of an amount of datato be transmitted from the terminal. The scheduling message can serve togrant transmission access to the terminal in dependence upon an amountof data received by the network resources, and on the indication of theamount of data to be transmitted in the data transfer request.

The data transfer request may include an indication that an amount ofdata greater than the data portion is to be transmitted from theterminal.

Resources allocated to the data transfer request, and to transmission ofthe data portion may be predetermined. Alternatively, the networkresources may determine resources allocated to the data transferrequest, and to transmission of the data portion. The network resourcesmay indicate to the terminal data portions that can be transmittedwithout a data transfer request.

The communications network may be a wireless network. In one embodiment,the communications network is a radio frequency network, and theterminal is a mobile terminal.

Other aspects of the present invention provide a terminal and a networkthat operate in a manner in accordance with the previous aspects of theinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates part of a wireless telecommunications network;

FIG. 2 illustrates mobile terminal used in the network of FIG. 1;

FIGS. 3 and 4 illustrate data structures for use in networks embodyingthe present invention; and

FIG. 5 is a flowchart describing steps in a method embodying anotheraspect of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 illustrates part of a wireless network which can be utilised inaccordance with the present invention. As described above, networkresources 3 communicate with mobile terminals 5 over an air interface 7.

FIG. 2 illustrates a mobile terminal 5, which includes a controller 10which receives inputs from input devices 12, and supplies data to betransmitted to a transmit/receive (TX/RX) unit 14. The transmit/receiveunit 14 transmits data over the air interface 7 via an antenna 16. Thetransmit/receive unit 14 also receives signals via the antenna 16 andcommunicates those to the controller 10. The input devices can be akeypad, microphone etc, and the output devices 13 can be a displaydevice and a loudspeaker. As is well known, a user of the mobileterminal 5 supplies voice signals and key inputs to the controller 10 inorder to perform voice calls and/or data calls.

The present invention is concerned with uplink transmission of data froma mobile terminal 5 to the network resources 3. In accordance with thepresent invention, in order to transmit data portions from the mobileterminal 5 to the network resources 3, the mobile terminal makes use ofboth contention-based techniques and scheduled techniques.

In the following, the term ‘chunk’ is used to denote the smallestresource allocation that can be assigned to a user. In case of OFDMA(Orthogonal Frequency Division Multiple Access), a chunk corresponds toa set of sub-carriers and a time interval and in case of FDMA (FrequencyDivision Multiple Access) a chunk would correspond to a frequency andtime interval. Different chunks can be reserved for specific usage, forexample, broadcast information, user data transmission or schedulingrequests.

In accordance with embodiments of the present invention, an uplinkresource is logically divided into three different sets (S1,S2,S3)(shown schematically in FIG. 3):

-   -   S1 is used for scheduling requests.    -   S2 is used for contention-based data transmission.    -   S3 is used for scheduled data transmissions.

Data transfer in accordance with the present invention will now bedescribed with reference to FIGS. 1 to 5. When a data portion is to betransmitted by the mobile terminal 5 to the network resources 3, themobile terminal 5 operates to transmit the data portion in thecontention-based set S2. The data portion is sent in set S2 without avalid scheduling message being received by the mobile terminal 5, and socollisions may occur for the set S2 for the data portion. Theprobability of collision may be relatively high.

In order to mitigate the effects of any collision for the data portionsent in set S2, the mobile terminal send a scheduling request in set S1(FIG. 5, step B) substantially simultaneously with the data portion inS2. The scheduling request may be subject to a collision, but since thescheduling request is small the probability of collision is low with areasonable size of set S1.

The network resources 3 determine whether the data portion concerned hasbeen received correctly (step C) and if so, the next data portion can betransmitted.

If the data portion has not been received correctly, then the networkresources 3 transmit a scheduling message (step D) to the mobileterminal 5, in order to schedule transmission of the data portion. Themobile terminal 5 is then able to transmit the data portion (step E) inset S3 in dependence upon the information supplied in the schedulingmessage.

A mobile terminal is only allowed to transmit data in set S3 if a validscheduling message has been issued to that mobile terminal. Thetransmissions in set S3 do not experience collisions since scheduling isused (assuming a reasonable scheduling strategy is used).

If there is a collision for the data portion sent in set S2, then thedata portion will be scheduled for transmission in set S3 by the networkresources. There are no retransmissions on the contention-based set S2and, so no random back off or other conflict resolution scheme isneeded. All retransmissions are under the control of the networkresources and use set S3.

The sets S1, S2, and S3 may be overlapping. However, in a preferredembodiment, S1 is orthogonal to both S2 and S3 to ensure that schedulingrequests do not interfere with data transmission (and vice versa). Inaddition, S2 can be orthogonal to S3.

In one embodiment, the scheduling request (sent in S1) may containexplicit information about the amount of data to be transferred from themobile terminal 5 to the network resources 3. When the network resourcesreceive a data portion in S2 and a corresponding scheduling request inS1, the network resources 3 subtract the amount of correctly receiveddata from the amount of data indicated in the scheduling request, andsend a scheduling grant for the remaining amount of data. When theamount of correctly received data is larger than or equal to the amountof data indicated in the scheduling request, the network resources donot send any scheduling message to the mobile terminal, since the dataportion is assumed to have been received correctly.

In another embodiment, the scheduling request contains a flag indicatingif the data portion to which the scheduling request corresponds containsall of the data to be transferred from the mobile terminal. When thenetwork resources 3 receive the scheduling request and correctly receivesome amount of data, the network resources identify from the indicatorflag in the scheduling request, whether or not additional data is to betransferred from the mobile terminal. If more data is to be transferred,the network resources send a scheduling message to the mobile terminalin order to allow the remaining data to be sent in a scheduled manner.

In a further embodiment, the scheduling request does not contain anyinformation about the amount of data to be transferred from the mobileterminal. In such an embodiment, the network resources do not havesufficient information to determine whether the mobile terminal hastransmitted all of its data or if more data remains to be transferred.The network resources can then send a scheduling message to allow anyadditional data to be sent in a scheduled manner from the mobileterminal.

In addition to the above mentioned information, the scheduling requestmay contain additional information to aid the scheduling decision in thenetwork, e.g. priority of the data to be transmitted, Quality of serviceclass or similar.

In a low load situation it can be beneficial to allocate a relativelylarge amount of resources for contention-based transmissions, i.e.defining a large set S2, since this would allow for low delays when datais transmitted.

In a high load situation, the contention-based transmissions in S2 wouldsuffer from frequent collisions. Also, the contention-basedtransmissions in S2 take resources from the scheduled transmissions inS3. It can, therefore, be beneficial in high load situations to allocatea larger part of the resources to scheduled transmissions, by notallowing any contention-based transmission at all, or by only allocatinga small amount of resources. Examples of such allocations areillustrated in FIGS. 3 and 4 respectively.

The allocation of resources between the different groups S1, S2, and S3can be realised in several ways, as will be described below.

The part of the total resources allocated for scheduling requests, S1,can either be specified as part of the standard or signalled by a partof the network resources responsible for the radio resource control.

The division between S2 and S3 can be handled in several ways:

One option is for the network resources 3 to divide semi-statically theavailable resources between S2 and S3. The division can then becommunicated to the mobile terminals. The division can be updated as thetraffic load changes, although reallocation of resources between S2 andS3 are likely to be slower than the scheduling decisions for the datatraffic. S2 and S3 can either be overlapping or orthogonal. In theformer case the network resources must take into account that anyscheduled transmission using chunks being part of both S2 and S3 couldbe interfered with by contention-based transmissions. In the latter case(of S2 and S3 being orthogonal) this problem is avoided.

Another option would be for the network resources 3 to divide the totalresources into S2 and S3, such that all mobile terminals in the area forwhich the network resources are responsible are provided with atransmission grant in advance (without a prior request phase) for the S2resources. That is, a terminal is provided with some grants in advance(e.g., at call setup or whenever the network so decides) and thosegrants give the terminal the right to transmit using the S2 resourceswithout a prior request

To transmit on S3, the terminal must request for permission using ascheduling request. This is one way of implementing a more ‘dynamic’division of resources between S2 and S3, the network can at any timedecide to, e.g., allocate more/less resources to S2 by sending new‘in-advance’ grants, i.e., using the same signalling mechanism as anywayused for scheduling.

Thus, any terminal with an advance grant can at any time starttransmitting on S2. In response to the scheduling request (and thecontention based transmission on S2), the scheduler can determine toassign the terminal a grant using S3 for the remaining part of thepacket and/or to revoke the advance grants for other terminals in thecell. Note that the terminal should only transmit a scheduling requestalong with the data transmission for the initial transmission using S2,nor for subsequent (scheduled transmissions on S3). Hence, the terminalbehaviour could be slightly different depending on whether an ‘advance’grant is used or a grant received in response to a scheduling request.

The terminal may also keep the network updated about its status, e.g.,remaining data in the buffers, during a scheduled transmission byincorporating this information in the normal data stream as a header.Thus, the network could schedule the UE to transmit using S3 for a longperiod of time and by observing the status of the terminal decidewhether is should reallocate resources to the terminal.

Embodiments of the invention make it possible to combine the propertiesof scheduled transmission and contention-based transmission. Suchcombination gives the following advantages:

-   -   Initial transmissions can be done immediately without waiting        for a scheduling message.    -   Small amounts of data can be sent with low delay without        scheduling.    -   In case of collisions the user will automatically be scheduled,        i.e. no back off mechanism creating delay is needed.

It should be noted that the above-mentioned embodiments illustraterather than limit the invention, and that those skilled in the art willbe capable of designing many alternative embodiments without departingfrom the scope of the invention as defined by the appended claims. Inthe claims, any reference signs placed in parentheses shall not beconstrued as limiting the claims. The words “comprising” and“comprises”, and the like, do not exclude the presence of elements orsteps other than those listed in any claim or the specification as awhole. The singular reference of an element does not exclude the pluralreference of such elements and vice-versa. The invention may beimplemented by means of hardware comprising several distinct elements,and by means of a suitably programmed computer, if appropriate. In aclaim enumerating several means, several of these means may be embodiedby one and the same item of hardware. The mere fact that certainmeasures are recited in mutually different dependent claims does notindicate that a combination of these measures cannot be used toadvantage.

1. A method in a network node for transmitting data between a terminaland a communications network, wherein the method comprises: receivingdata and a data transfer scheduling request transmitted substantiallysimultaneously by a terminal, the data transfer scheduling requestrelating to said data; transmitting a scheduling message to the terminalif the data is not received completely; and receiving data from theterminal according to parameters indicated in said scheduling message.2. A method as claimed in claim 1, wherein the data transfer schedulingrequest includes an indication of an amount of data to be transmittedfrom the terminal.
 3. A method as claimed in claim 2, wherein thescheduling message serves to grant transmission access to the terminalin dependence upon an amount of data received by the network resources,and on the indication of the amount of data to be transmitted in thedata transfer scheduling request.
 4. A method as claimed in claim 1,wherein the data transfer scheduling request includes an indication thatan amount of data greater than the data portion is to be transmittedfrom the terminal.
 5. A method as claimed in claim 1, wherein resourcesallocated to the data transfer scheduling request, and to transmissionof the data portion are predetermined.
 6. A method as claimed in claim1, wherein resources allocated to the data transfer scheduling request,and to transmission of the data portion are determined by the networkresources.
 7. A method as claimed in claim 1, wherein the networkindicates to the terminal which data portions that can be transmittedwithout a data transfer scheduling request.
 8. A method as claimed inclaim 1, wherein the communications network is a Wireless network.
 9. Amethod as claimed in claim 8, wherein the communications network is aradio frequency network, and the terminal is a mobile terminal.
 10. Anetwork node for communicating with terminals via a contention-baseddata transmission, the network node operable to: receive data and a datatransfer scheduling request relating to the data transmittedsubstantially simultaneously from a terminal; transmit a schedulingmessage to the terminal, if the data is not received completely; andreceive data from the terminal transmitted according to parametersindicated in said scheduling message.
 11. A network node as claimed inclaim 10, wherein the data transfer scheduling request includes anindication of an amount of data to be transmitted from the terminal. 12.A network node as claimed in claim 11, wherein the scheduling messageserves to grant transmission access to the terminal in dependence uponan amount of data received by the network resources, and on theindication of the amount of data to be transmitted in the data transferscheduling request.
 13. A network node as claimed in claim 10, theapparatus being configured to operate in a wireless network.
 14. Anetwork node as claimed in claim 13, wherein the wireless network is aradio frequency network, and the terminal is a mobile terminal.
 15. Amethod in a terminal for communicating with resources of atelecommunication network, the method comprising: transmitting data tothe network substantially simultaneously with a data transfer schedulingrequest relating to the data; receiving a scheduling message from thenetwork indicating that the data was not received completely by thenetwork; and transmitting data to the network according to parametersindicated in the scheduling message.
 16. A method as claimed in claim15, wherein the data transfer scheduling request includes an indicationof an amount of data to be transmitted by the terminal.
 17. A method asclaimed in claim 16, wherein the scheduling message serves to granttransmission access to the terminal in dependence upon an amount of datareceived by the network resources, and on the indication of the amountof data to be transmitted in the data transfer scheduling request.
 18. Amethod as claimed in claim 15, wherein the data transfer schedulingrequest includes an indication that an amount of data greater than thedata portion is to be transmitted from the terminal.
 19. A method asclaimed in claim 15, wherein transmitting the data portion and the datatransfer scheduling request comprises wirelessly transmitting thescheduling message.
 20. A method as claimed in claim 19, whereinwirelessly transmitting the scheduling message comprises transmittingthe scheduling message to a mobile terminal operating in a radiofrequency network.
 21. A terminal for a communications system, operableto: transmit data to the network resources substantially simultaneouslywith a data transfer scheduling request relating to the data; receive ascheduling message transmitted by the network resources indicating thatthe data was not received completely by the network resources; andtransmit data to the network resources according to parameters indicatedin the scheduling message.
 22. A terminal as claimed in claim 21,wherein the data transfer scheduling request includes an indication ofan amount of data to be transmitted from the terminal.
 23. A terminal asclaimed in claim 21, wherein the data transfer scheduling requestincludes an indication that an amount of data greater than the dataportion is to be transmitted from the terminal.
 24. A terminal asclaimed in claim 21, wherein the communications system is a radiofrequency wireless network, the terminal being a mobile terminal.